Magnetic recorder head



Patented Aug. 16, 1949 MAGNETIC RECORDER HEAD Marvin Cainras, Chicago, lll., assignor to Armour Research Foundation of Illinois Institute of Technology, a corporation oflllinois Appncation March 17, 1945,'seriai No. 533,317.V

This invention relates to a magnetic head which may be used for recording or reproducing or both, and more particularly to a magnetic head of low impedance for recording longitudinally on' a traveling record medium and reproducing previously longitudinally recorded records. One of the principal features and objects of the present invention' is to provide the recording and reproducing yhead of low impedance which is extremely low in cost but which will nevertheless efficiently magnetize a traveling record medium longitudinally thereof and reproduce longitudinal recordings on traveling record medium which have previously been magnetized. I A further object of the present invention is to provide a novel recording and' reproducing head which may be quickly and easily mounted in place, removed and replaced Without necessitate ing any soldering or complicatedrconnections of lead wires and so forth.

Another object of the present invention is to provide a novel recording and reproducing head in which the magnetizing and energy receiving element thereof is in the form of a single turret or a part of a single turret.

Another and further object of the present in'- vention is :to provide a novel recording head in which the circular field about a straight current-r conducting element is employed to effect longitudinal magnetization of a traveling record medium. Another and still further object ofthe present invention is to provide a novel recording and reproducing head in which the energizing coilv is in the form of a substantially straight currentconducting element mounted in a. core member formed of a substantially flat sheet of material of relatively high magnetic permeability and relatively low magnetic retentivity and which current-conducting element is disposed substantially at right angles to the sheet.

Still another and further object of the present invention is to provide a novel mounting for receiving and electrically connecting a magnetic recording or reproducing head.

Still a further object ofthe present'invention is to provide a novel method of magnetic recording and reproducing.

vThe novel features which are believed vto be characteristic of my invention are set forth with particularity in the appended claims. My inven-V tion itself, however, both as to its organization, manner of construction, and method of operation, together with further objects and advantages thereof, may best be understood with .reference 7 Claims. .(01. 17e-'1002 p to the following description, taken in connection with the accompanying drawing, in which:

Figure 1 is an isometric view of the core mem-. ber of a recording andreproducing head embodying the novel features of the present invention;

- Figure 2 is ardiagrlamrnatic view showing the core member of Figure 1 with an energizing mem-'- ber mounted therein and electrically connected toY the force ofuctuating energy when the head is being used `as a recorder and to the reproduce ing circuit when thehead is being used as a reproducer; i

Figure 3 is a sectional view through the recorder head in proximity to the wire guiding groove `but, through; the current-conducting member; Y

Figureflisa view similarto Figure 3 showing the recorder head in mounted position, the sectional view being taken substantially along the line IV--IV of vFigure 5; and i Figure 5 is an e nd elevationalrview of the recording head in mounted position.

Referringrst to Figures 1 `and 2 of the drawing, the recording and reproducinghead of the illustrated embodimentV comprises a core member I0 which may bein the form of a vstamping of any suitable material having relatively high permeability and relatively low magnetic retentivity. This member l0 is in the form of a small flat plate one edge of which iscrowned as at II to facilitate the entry of a traveling record medium such as wire in the wireeguiding groove I2 which is kformed alongV the crowned edge II. A slot I3 is cut in the plate I0 approximately mid-way along the crowned edgev I I. This slot I3 is arranged to receive a current-conducting element I 4 which may conveniently be of copper or silver in the form of a thin shim'or-strip of such material. It is to be understood that the drawing is very greatly enlarged from the actual size of the recording head and is not made to scale in orderto emphasize the Various novel features of the present invention. I n practice it has been found that a core member may conveniently be approximately three-eighths vof an inch long and a quarter of an inch high (that is, fro-m its bottom edge to its crowned edge). It has further been found that the slot I3 may conveniently be approximately .0,02 inch in width. It will, of course, vbe understood that these dimensions are merely given by way of example t0 show one particular embodiment of the invention and to give some idea of the relative order of magnitude of the recorder head. Y .v

Referring now specifically to Figure 2 the Iunc-IVv tional operation of the recording head will now be described and thereafter a specific physical embodiment of the recorder head Will be described. If the current-conducting element I4 is electrically connected at its opposite ends to the low impedance winding I of a transformer I6, and fluctuating electric energy is supplied to the high impedance winding I'I of the transformer I6', the current flowing through the current-conducting element I4 will set up a magnetic field at right angles thereto as indicated by the ux lines I9. This is merely the usual system of magnetifields which surround a current-conducting element when current is flowing therethrough. The cir-V cular magnetic field is at right angles'to current-conducting element. Due to the positioning of the current-conductingy element I4 with respect to the core Il), it will be observed that the eld will be greatly concentrated in the region of the gap formed by the slot I3 which lies between thecurrent-conducting el-ement I4 andlv the crowned edge II. The liux lines in the other region around the current-conducting element VI 4 are spread out, however, due to the fact that the core member |01' provides a low reluctance path for the flux. The bunchi'ng of the flux lines or, in otherwords, the concentrationof themagnetic eld at the open-portion of the slot I3 in effect causes the confronting Vportions I9 and 2l) of the slot `I3 to be confronting polar portion or pole pieces. It will be noted: that 'all' of the 'flux lines across the gap between the polar portions I9 and 29 lie in substantially the same direction and more particularly substantially longitudinally of the wire 21 which is traveling through the groove I 2 in the crowned edge I I of the core piece III. This causes longitudinal magnetization-of the wire or record medium 2Il notwithstanding the fact thatno polesin the usualV sense are" provided and notwithstanding the fact that no -solenoid type energizing Vcoil is: provided.

In practice the wind-ing t5 of the-transformer I6 should/preferably match the impedance of --the current-conducting element I4 and where the current-conducting element |14- 'is' of extremely good electrical conductivity, the windingv If5 will usually be a single turn winding on the transformer I6.

I-trhas been-found in' practice that' very much better results` are obtained when theL conductors 22l andi 23 which connect the current-conducting element I4 tothe winding I-5 of the transformer I6 are in the form of a loop whichcompletely surrounds the wire 2li. In other- Words, it has been found muchl more satisfactoryl toV connect the winding I5, the conductorsV 22 and 23. andthe conductor I4 in a closed loop around the wire 2li than it has been to connectthese same elements in a closed loop with the wire- 2I completely outside of the loop;

It is believed that the explanation of' this phenomenon is that when the closed' `loop :surrounds the wire only a small percentage of the ux due to stray elds threads the pickL-up, loop on reproduction. When thel closed loopldoes not surround the wire but ratherL surrounds the-bulkn` ofthe core member III, a large percentagev of the stray flux threads` the loop and greater` distortion. results. This applies not-only to the humv fieldsbut to the-fields of the-wire itself which are just outside of the recording head.

The above functional operation of: the device has" been a description ofthe device when. it is operating as a recording head. 'It willalso oper ate in an extremely satisfactory' manner/'as a Y phys-ical 7embodiment of the device.

eration of my invention and the novel method thereof, reference will now be made to a specific A Opposite sides of the core member Ill, which has been de- .described in connection with Figures 1 and 2, are

provided with a Vlayer of insulating paper 28 and on ltop of the papers 28 are secured copper `plates 29. The copper plates 29 are recessed or cut back as at 30 adjacent the current-conducting element I4 and solder is then poured into this cut-back portion 39. The result is'that-the: current-conducting plates 2-9' are electrically connected to the current-conducting element I4. This has beenxfounjd to' forma very satisfactory way to` electrically connect termi-nal members tothecurrent-conducting member I4. In this instance, ythe terminal members are, of course, the conducting` plates29. This assembly forms a unit which. canfbeconveniently and easily slipped into a head supporting structure as shown: in Figures 4' and 5 which .include a pair of ccnducting plates 3ly mounted on an insulating support` 32 and springypressedas at 33. The cur rent-conducting platesv 3| which may conveninetly be formed of copper orthe'like form avgood. el'ecf trical contact with the plates 29 and provide, due to their area, relatively low contact resistance. The leaf springs 33v urge' theplates 3| toward each other and.y thereby tightly grip the head structure. The conductors which lead tothe amplifying apparatus are permanently connected (not shown) to the.:conducting yplates 3 I'. As may be seen best inrFigure 5; the upper edgeV ofthe plates 3l are rolled back slightly as at 34 in order that the head may be quickly-and easily inserted between the y plates 3|. Wheny it is desired to replace the head structure' generally designated by the reference numeral 3,5 inA Figure 3, it is gripped at its op'- po'site ends and quickly removedk from between the plates 3l. In this connection, it will be noted thatthe plates 3l areslightly shorter than the length of the head structure 35 in order to` facilitate gripping of thesame. A new heady may be then easily inserted between the plates 31'.. No soldering or other electrical connection of a permanent nature'mayibe made sincel the new head makes its electrical contact by virtue of the facty that the conducting 'plates 29 of the Ahead structure 351liev againstfthe plates 3l' of thehead` supporting structure.

While: I have shownaaA particular embodiment of my invention and describeda particular method of operation,.itwill, of course, be'understood that Ido not wishto be. limited thereto; since many modifications n'i'ay'ben'iadeV and I, therefore, contemplate by the appended claimslto cover all such modica-tionsas fall within the spirit and scope or my invention'.

arranged to conduct a fluctuating magnetizing current to be recorded and to have induced therein a uctuating current from a magnetized reccrd medium, a sheet of electrical insulating material on both sides of said first member, and a pair of electrical conducting plates on the outer sides of each insulating sheet, said electrical conducting plate being electrically connected to the opposite ends of said second member.

2. A magnetic head assembly comprising a paramagnetic core member, an electromagnetic circuit associated with said core member, and a pair of electrical conducting plates on opposite sides of said core member and connected respectively to the opposite ends of said electromagnetic circuit, thereby providing terminal members therefor, said core, said circuit and said plate forming an integral unit, and a second pair of electrical conducting plates between which said unit is tightly nestled, whereby permanent circuit connections may be made to said second pair of electrical conducting plates and whereby said integral units may be readily and quickly inserted and removed.

3. A magnetic head assembly comprising a paramagnetic core member, an electromagnetic circuit associated with said core member, and a pair of electrical conducting plates on opposite sides of said core member and connected respectively to the opposite ends of said electromagnetic circuit extending through said core member, thereby providing terminal members therefor, said core, said circuit and said plate forming an integral unit, a second pair of electrical conducting plates, a base upon which said second pair of electrical conducting plates is mounted, and resilient means urging said second pair of electrical conducting plates toward each other, whereby said integral units may be inserted between said second pair of plates with said rst pair of plates in good electrical conducting relation with said second Ypair of plates.

4. A magnetic recording and reproducing head comprising a member of relatively high magnetic permeability and relatively low magnetic retentivity, a sheet of insulating material on opposite sides of said member, electrical conducting plates on opposite sides of saidrmember and separated therefrom by said sheets of insulating material, and a member of good electrical conductivity extending through said member, said sheet and said plate, said second member of good electrical conductivity terminating adjacent the outer surface of each of said plates and electrical bonding material securing said opposite ends of said second member to said plate.

5. A magnetic transducer head comprising a core of relatively high magnetic permeability and relatively low magnetic retentivity, said core having a gap therein extending inwardly from one edge to define a pair of confronting magnetic poles, and a single current-carrying conductor disposed in said gap itself between said confronting poles, said one edge of said core being arranged to have a magnetic record medium passed therealong across said gap.

6. A magnetic transducer head comprising a core of relatively high magnetic permeability and relatively low magnetic retentivity, said core having a gap therein extending inwardly from one edge to define a pair of confronting magnetic poles, and a single current-carrying conductor disposed in said gap itself between said confronting poles, said one edge of said core being arranged to have a magnetic record medium passed 2o therealong across said gap, and an energizing circuit for said conductor forming a closed loop around the path of travel of said record medium.

7. A magnetic transducer head comprising a core of relatively high magnetic permeability and relatively low magnetic retentivity, said core having a gap therein extending inwardly from one edge to define a pair of confronting magnetic poles, and a single current-carrying conductor disposed in said gap itself between said confronting poles, said one edge of said core being arranged to have a magnetic record medium passed therealong across said gap, said conductor being spaced inwardly from the path of travel of said record medium and substantially lling the remaining portion of said slot.

MARVIN CAMRAS.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS 

